Re: [Qemu-devel] Linux kernel polling for QEMU

[Eliezer Tamir <eliezer.tamir@linux.intel.com>]

+ Eric, Willem

On 24/11/2016 17:12, Stefan Hajnoczi wrote:
> I looked through the socket SO_BUSY_POLL and blk_mq poll support in
> recent Linux kernels with an eye towards integrating the ongoing QEMU
> polling work.  The main missing feature is eventfd polling support which
> I describe below.
...
> State of polling in Linux
> -------------------------
> SO_BUSY_POLL causes recvmsg(2), select(2), and poll(2) family system
> calls to spin awaiting new receive packets.  From what I can tell epoll
> is not supported so that system call will sleep without polling.

At the time I sent out an RFC for epoll() SO_BUSY_POLL support.
https://lkml.org/lkml/2013/8/21/192

In hindsight I think the way I tracked sockets was over-complicated.
What I would do today would be to extend the API to allow the user
to tell epoll which socket/queue combinations are interesting.

I would love to collaborate on this with you, though I must confess that
my resources at the moment are limited and the setup I used for testing
no longer exists.

-Eliezer